A wireless ABS (anti-skid brake system) sensor system has been suggested, in which sensor signals generated from a revolution sensor mounted on a wheel support bearing assembly is transmitted by wireless between a vehicle wheel and an automotive body to thereby eliminate the use of harnesses. On the other hand, the Japanese Laid-open Patent Publication No. 2003-146196, published May 21, 2003, discloses the system in which in a wheel support bearing assembly equipped with a revolution sensor, output signals of which are transmitted by wireless, the presence or absence of an abnormality in the revolution sensor is determined by means of a self-diagnosing circuit and an abnormality indication signal when generated from such circuit can be transmitted by wireless. Those suggestions require that supply of an electric power to the revolution sensor and also to a wireless transmitting system to be provided for by the revolution sensor that concurrently serves as an electric power generator but supply of an electric power by wireless from an outside power source is also referred to in those suggestions.